Process for refining mineral oil



Patented time 29, 1937 UNITED STATES 2,085,518" r I raocnss ,FQRREFINING mans], OIL

Willem J. D. vanDijck, The Hague, Netherlands,

assignor to Shell PATENT OFFICE Development Company, San

Francisco, Calif., a corporation of Delaware v No Drawing.ApplicationFebrua -y 18, 1935, Se-

rgal No. 7,072. In the Netherlands March 19,

Myinvention relates to a process forsep arating liquid hydrocarbonmixtures into relatively more highly and less highly parafiinic portionsby extraction with selective solvents. More particularly, the presentinvention relates to a methd of improvingthe extraction process; by theaddition of a diluent to the selective solvent.

It is known that mineral oils, such as lubricating oils, transformeroils, spindle oils, kerosene,

l0 gasoline,etc.,:;as well as non-mineral oils can be treated withselective solvents to effect a separationbetween components of differingcharacteristics. Thus, a lubricating oil may befreed from all or asubstantial part of its non-parafiinic components; such as aromatics,naphthenes and olefines, by treating it with. certain selective solventswhich havea preferential solubility for the non-parailinic componentsunder conditions producing two phases, separating, the phases,

and distilling themlseparately to recover thesolvent from each of thephases. Numerous solvents and solventmixtures have been proposed forthis purpose. Among these are furfural and various solvent mixturescontaining furfural in combination with a diluent. I I

The degree of selectivity of furfural, either alone, crin the knownmixtures, is not sumciently great to effect thehigh degree of separationand high yield often desirable in commercial operations. It was alsofound that dark-coloured con'stituentsof hydrocarbon mixtures are "noteffectively removed by these solvents. Moreover, difliculty is oftenexperienced in recovering the furfural from the separatedphases becausethe boiling point of furfural is so high that at the temperatures ofdistillation decomposition of the furiural, or polymerization, or evenreaction with the hydrocarbons or with the impurities carried by theinisbrought about. This difficulty is characterized bya lossof'thesolventand by the formation of undesirable and non-readily separabledark-coloured impurities.

In accordance with my invention I overcome all r of these defects to alarge extent by treating the a hydrocarbon oils with furfural in thepresence of naphthalene, In carrying out my invention, I, bring thehydrocarbonmixture into intimate contacti'with furfural in an extractionzone in 50 the presence of naphthalene, which maybe in+ r ctroduced,separately, or together with the fur fural or with the hydrocarbonmixture.

I may employ any suitable form of, apparatus, such as "a singleagitating and settling zone, a

55 series of agitators and phase separators, or a flow countercurrentlyto 'duosol process.

most readily single or multistage countercurrent treater. The

quantity of furfural and ahead the temperature are controlled to producetwo phases, andtoproduce the desired yield, as is well known in the art.In countercurrent processes it is preferable to introduce all or asubstantial part of the naphthalene into theprocess with the furiural orat a point near the point at whichthe raflinate or solvent-poor phase iswithdrawn. This raffinate phase is poor in furfural and naphthalene, andcontains mainly parafflnic constituents oi the hydrocarbon mixtureandmay, after its withdrawal from the extraction zone, be treated toseparate it intosolvent and oil portions. Theextract phase, which isrich in solvent, conand naphthalene. v vI may operate my extractionprocess in accordance with any of a large number of known erties, of thetreated hydrocarbons and therequired purity of the end products. Forexample, I may employ a batch process, or a continuous orsemi-continuousmode of operation. I may, moreover, use-my solvent with anadditionalsolvent which is caused to 'the furfural mixture, such aprocess being commonly known as the I may subject the mixture to beextracted to a preliminaryextraction under the same or less intenseconditions! The extraction efficiency may be further improved by usingtemperature regulating means to provide a gradually decreasingtemperature in the direcmixture in connection tion of flow of theIurfural, as is well known in the art. I may also subject the extractsolution obtained by treating the liquid hydrocarbon mixture withfurfural and naphthalene, to the washing action of a liquid entirely orsubstantially consisting of the components or groups of componentsof[the liquid mixture which are Saidliquid maybe apart of the solution ofextract in extracting agent(s) from which the extracting agent has beenentirely or substantiallyremoved aim which has been'obtaine'd after theabove-mentioned washing action has been applied to it. Inallthese modesof extraction, the naphthadissolving in theextracting agent.

lene exerts a favourable efi'ect on thedistribu tion of the paraflinicand non-paraffinic compoproduced at the operat- Compared with thelighter nents between the phases ing temperature.

15 tainsylarge amounts of non-parafiinic constitu ents, and is alsotreatedto remove thefurfural 20 methods to suit local conditionsspecific propdiluents, such as benzene or ether, naphthalene ,andextract phases. The mixing ratio of furfural andnaphthalene maybevaried, and is not limited to the ratiogiven in the appended example.The

tity, as used in the claims, I mean such a quan- H tity of naphthaleneas will substantially improve Y maximum quantity of naphthalene isdetermined by the solubility of the naphthalene at the extractiontemperature to be employed in a particular situation. By-the termeffective quanthe extraction characteristics for the particularconditions encountered, it being understood that this quantity may bedetermined readily by one skilled in the art.

It may sometimes be advantageous to withdraw at least a portion of theextract phase or extractionmixture at an intermediate point of the extraction zone (e. g., from an intermediate point oi a countercurrentcolumn or between two adjacent phase separating and mixing devices), re-

move at least a portion of the naphthalene from the withdrawnsubstances, and return the residual portion ofthe withdrawn extractionmixture to c the extraction zone nearthe point where the substances werewithdrawn. By repeating this operation at successive points of theextraction 80 zone, the effect ofa progressively decreasingconcentration of the napthalene in the direction of how of theextractphase-can be obtained, which may often further improvethe extractionefficiency of my process. This'method of removing the diluentatsuccessive points is more fully described and claimed in mycopendingapplicm,

tion, Serial No. 11,647,-filed March'18, 1935. .The napthalene andfurfural may be recovered fromthe separated phases or from the withdrawnextraction mixture either as a mixture of solvents. orseparately,asdesired. The recovery of the-solvent may be effected by any suitablemethod, such as distillation or washing with a suitable solvent, such as45% ethyl alcohol, etc. I have found that the presence of thenaphthalene makes it easier to recover the furfural bydistillation,-.andthat overheating and the consequent formation of,non-readily removable impurities is minimized when an oil containing thesolvent mixture of my invention-isdistilled.

I My ,inventionfinds especial utility in the extraction oflubricatingoils to produce oils having fiatftemperature viscosity,curves (i.. e. having high, viscosity indices and which are free fromobjectionable colouring -matter. otan extraction process of this typemay be expressed. in terms oithe quantityand quality of the rafllnate.'Thus, while it is possibleto produce rafiinates oi'almostany desiredviscosity index; the yield. will generally be. low. Therefore, foragiven quality of the product, the yie'ld is a measure of the efliciencyoi the extraction. Simi- 1'arly,'for a given yield, theefii'ciency oithe extrac tion may be measured tinterms of the quality,(viscosityindex) oi the product.

By conducting the extraction in accordance with the presentinvention, 1. e. by using furfural in the presence of naphthalene, itbecomes possible toimprove the quality and/or quantity of the oilrafiinate and to conserve the furfu'ralQ Themarlred improvementobtainable from my solvent mixture may be understood from the followingexample, which it'ls understoodis exemplary only.

A Venezuelan lubricating oil distillate having The efliciency aviscosity, in centistokes, of 53.6 at 210 F. and 3180 at 100 F. wasextracted in four consecutive stages with an equal volume of a mixtureof 70% by weight furfural and 30% of naphthalene under conditions toproduce a yield of 85% by weight of raflinate at each stage. Thetemperatures at the'successive stages were 25, 35, 55 and 65 C.respectively. A final solvent-free rafilnate of 50% by weight of theinitial oil was obtained. The viscosities of this raflinate at 210 F.and 100 F. were 31.1 and 710 respectively, which correspond to aviscosity index (Deen and Davis) of 69.

Upon extracting the same oil in four consecutive stages with an equalvolume of furfural, but without the presence of naphthalene, underconditions to produce .the'same yield of ramnate as in the abovedescribed extraction with furiural and naphthalene, the viscosities ofthe produced rafiinate at 210 F. and 100 F. were 32.1 and 944respectively. These viscosities correspond to a viscosity indexof 45.

These results show that the efliciency of the extraction was decidedlyimproved by the use of a mixture of naphthalene and furfural. Besidesresulting in an improvedviscosity index, my furfural naphthalene mixtureremoved the darkcoloured constituents of the oil more completely andmore readily. Thus, in the above example, when the oil was extractedwith the furfural naphthalene mixture, after the first stage of theextraction 50% of the dark-coloured constituents appeared to have beenremoved; but only 40% were removed after the first stage when extractingwith iurfural in the absence of naphthalene.

As used in the present specification and claims there is no differencebetween .solution and mixture.

I claim as my invention:

1. In an extraction process for separating liquid hydrocarbon mixturesinto their component groups, the steps of extracting the mixture withfurfural in the presence of an efiective quantity of naphthalene toproduce-two liquid phases, and

separating the said phases.

oil comprising extracting the oil at least once with a selective solventto produce a liquid raffinate containing a.v smaller amount ofaromatics, and then further reducing the aromatic content of saidrafiinate by extracting said rafiinate with iurfural and in the presenceof an effective quantity or naphthalene 'to produce liquid raffinate andextract phases, and separating the said phases;

, 5. In an extraction processior separating hydrocarbon mixturesintotheir components, the steps of extracting the mixture with furfuralin lene under conditions producing a liquid raflinate and a liquidextract phase, separating the phases, anddistilling at least one of saidphases to recover the furiural.

6. In an extraction process for treating hydrocarbon mixtures, the stepsof flowing a hydrothe presence of an effective quantity ofnaphthacarboumixture countercu'rrently to andin intimate contact withconcurrent and commingled streams of furfural and naphthalene underconditions producing liquid raflinate and extract phases, andseparatingsaid two phases.

7.In an extraction process for separating hydrocarbon mixtures intotheir components, the steps of extracting the mixture with furfural inthe presence of an effective quantity of naphtha- 2,osa,u1s t Y 3 leneunder conditions producing a liquid ratfinate phase and a liquid extractphase, separating the phases, and washing at least one ofsaidphases witha selective solvent for furfural to separate the furfural from thehydrocarbons. l

8. The process according to claim 7 in which the selective solvent forfurfurai is aqueous ethyl alcohol.

WILLEM J D. VAN DIJCK.

